Production of artificial filaments and like materials



March 2, 1937. H. DREYFUS PRODUCTION OF ARTIFICIAL FILAMENTS AND LIKE MATERIALS Filed May 18, 1934 Patented Mar. 2, 1937 UNITED STATES PRODUCTION F ARTIFCIAL FILAMENTS AND' LIKE MATERIALS Henry Dreyfus, London, England Application May 18, 1934, Serial No. 726,275

In Great Britain May 24, 1933 7 Claims.

This invention relates to the production of artiiicial iilaments and like materials, and particularly to the production of such materials by the dry or evaporative method, according to which a spinning solution of the basic material in a suitable solvent liquid is extruded through a spinning jet into an evaporative atmosphere Where the solvent is eliminated.

The usual apparatus for carrying out this process consists in a vertical spinning cell provided with heating means which bring air admitted into the cell to the required temperature, the spinning jet being arranged near the top of the cell so that the laments or the like extruded from the jet pass downwardly to an aperture located at or near the bottom of the cell, from which aperture they are led to a winding or twisting and winding device. In a very common construction of cell the jet is carried by a candle filter arranged inside the cell, and, following the arrangement described in U. S. Patent No. 1,602,125, the hot air which ascends to the top of the cell exerts a considerable heating effect upon the spinning solution passing through the filter candle on its way to the jet.

With the continued increase in the rate of production rendered possible by improvements in the dry-spinning operation and the consequent increased rate of flow of spinning solution to the jet, a lesser degree of heating of the spinning solution takes place, and for any particular size of filter and arrangement of pipes leading the solution to the jet the temperature diiierence between the spinning solution when extruded and the hot air at the top of the cell becomes more marked. Even though the lower temperature of the spinning solution is not necessarily prejudicial to the actual operations of extrusion and evaporation in the cell, the spinning solution may not be heated sufficiently to bring it to the degree of fluidity which enables the filter to exert to the best effect the homogenizing action which it performs prior to extrusion in addition to its filtering function.

It is the object of the present invention to devise a filter member which will enable full use to be made of the heating capacity of the air in the cell on the spinning solution on its way to the jet so as to bring the solution into the best condition for rapid, stable spinning.

According to the invention, a filter member is provided which is removed from the neighbourhood of the jet, and is arranged so as to be reached by hotter air in the cell. At the same time the dimensions of the filter member are inbil creased to enable greater heating to be obtained, these dimensions depending for one thing upon the output of the cell measured in terms of quantity of spinning solution extruded. Such filter member may, for example, be situated relatively close to one wall of the cell so as to receive the full effect of the current of hot air proceeding upwards from the heating means which, as mentioned before, are arranged near the sides of the cell. This disposition of the filter member not only enables it to be located so as not to interfere with ordinary access to the spinning jet and to be easily reached for attention such as cleaning-a. point of considerable importancebut also allows it to have such dimensions, particularly in the matter of length, as will allow adequate filtering or heat exchange surface without disturbing the position of the spinning jet, which then remains suitably near the top of the cell to allow the extruded filaments to have the maximum possible length of drying run within the cell.

If desired the filter member or filter body may be connected in series to a filter candle mounted in the usual place and serving as a jet support. When such an arrangement is employed, due4 regard should be paid in determining the dimensions of the filter member according to the invention or the dimensions of the filter candle, or preliminary filter body, to ensure that theA combined action of the two results in bringing the spinning solution to the required state of iiuidity in accordance with the particular spinning conditions prevailing. Alternatively, the lilter candle may be used as or replaced by a mere heater if the filtering capacity of the filter member is adequate, such arrangement increasing the liuidity of the solution before filtration commences. Further, in some circumstances, the filter candle may be dispensed with altogether and replaced by a pipe leading the spinning solution to the filter member.

As previously stated, the filtration is affected by the quantity of spinning solution passing to the jet, and it may, moreover, be influenced by the particular characteristics of the spinning solution itself. By the use of the iilter member according toi the invention, solutions of higher concentration, and consequently increased viscosity, can be readily brought to a condition for ready and complete filtration. Again, the filtration is affected by the viscosity of the cellulose acetate or other cellulose derivative dissolved in the solution, particularly when the solutions are 'of high concentration, and again the invention is of particular advantage in enabling' solutions of such materials to be readily ltered.

A convenient form of iilter member comprises a long cylindrical casing containing an internal pipe running along its length, the walls of the pipe being perforated, and covered with a filtering medium, such as a fabric of suitable weave. 'Ihe solution passes into the annular space between the pipe and the casing, through the filtering medium and the periorations to` the interior of the pipe, and out of the pipe. 1t is preferable that the inner tube should only be perforated over a part of its length, so that ltration does not occur immediately uponentry of the spinning solution into the lter member. Thus, the filtering material may cover approximately the half of the tube remote from entry, the tube only being perforated in this half. The tube, of course, is completely closed at its one end so that the whole of the spinning solution is forced to pass through the filtering material. If, however, the filter member is arranged so that entry of the spinning solution takes place at the opposite end to the outlet, the ltering material may be arranged over any part of the tube and may even cover its whole length since any tendency to short circuiting of the spinning solution is largely avoided.

In view of the adequate heating of the spinning solution which may be obtained by the device according to the invention by suitably dimensioning the device in accordance with the characteristics of the solution and the rate of flow of the solution, it is even possible to bring the solution to a temperature higher than that immediately adjacent the nozzle, for, although the solution may have a somewhat lower temperature than the air which is used to heat it, it can be so efliciently heated that, if desired, the temperature difference is less than the temperature drop of the air due to evaporation of the extruded solution.

It has already been mentioned that other cellulose derivatives than cellulose acetate may be used in the spinning solution. As examples of these may be cited other cellulose esters, e. g. cellulose formate. propionate, and butyrate, and cellulose ethers, e. g. ethyl and benzyl cellulose, and particularly those of high viscosity.

By way of example the invention will now be described in greater detail with reference to the accompanying drawing in Which:-

Figure 1 is a sectional side elevation of a spinning apparatus tted with lter according to the present invention;

Figure 2 is a sectional plan view of Figure 1.

Figure 3 is a view on a larger scale of the iilter and its connections as employed in Figure 1; and

Figure 4 is a sectional side elevation showing another method of fitting the iilter.

Referring to Figures 1-3 a spinning cell t is tted with a supply pipe 'I conducting spinning solution into a preliminary ltering body or filter candle 8. From the body 3 the solution proceeds through a connecting piece d and a pipe II) to the lter member or lter body II which is disposed, as shown in Figure 2, in the corner of the spinning cell 6 and close to the heating pipes I2, banks of which are disposed at the front and back of the cell. Figure 2 also shows the cell 6 to be one of a series of cells to which the banks of pipes I2 are common, the pipes running the whole length of the series. The ltered spinning solution returns from the lter body I I by means of a pipe I3 to the connecting piece 9 and is extruded through a spinning jet I4 in the form of filaments I5. The laments are passed round a guide I6 and are led from the spinning cell 6 to afeed roller Il conducting them to the guide i3 of a cap spinning device I9 by means of which they are twisted and wound.

Figure 3 shows the filter body II and its connections in greater detail. The filter body consists of a long cylindrical casing 2i) fitted at one end with a plug 2l into which is screwed an inner pipe 22 extending along the length of the cylindrical casing. The other end of the cylindrical casing is closed by means of a plug 23. The inner pipe is perforated over the lower half of its length at 2li so as to provide a passage between the annular space between it and the cylindrical casing 20, and its interior, and filtering medium 25 is secured round the perforated part of the pipe, the dimensions of the two members and the thickness of the filtering medium being such that a narrow annular passage is left for the spinning solution along the inside of the casing 20. The lower end of the tubel 22 is closed by means of a plug 26.

In the plug 2| a passage 2'! is provided for the i connection of a pipe I by means of a suitable union 29, the pipe i@ being connected at its upper end by means of a union 30 to the connecting piece 9. The pipe 30 communicates with a passage 3l in the connecting piece which passage in turn communicates with the preliminary filtering body 8. A central passage 32 in the plug 2I is connected by means of a union 33 to a pipe I3 leading through a union 35 to the lower part of the connecting piece 9. The spinning jet I is secured to the lower part of the connecting piece 9 and communicates with the pip-e I3. An insulated dividing pad S6 is provided in the middle of the connecting piece 9 to prevent heat exchange between the spinning solution about to pass into the jet Id and the spinning solution coming from the preliminary nltering body 8.

rIhe above described arrangement constitutes a filter having a high efficiency as a heat exchanger and the advantage of the rapid heat transfer rendered possible by the solution flowing as a thin stream while being heated immediately prior to filtration enables the whole device to be of relatively small size and so able to be placed where it will be surrounded only by the hottest air in the cell.

The spinning solution is delivered first to the annular space between the outside casing 2li and the inner pipe 22 so that it is subjected to the heating effect of the outside air while passing down the casing and before filtration takes place. Since only the lower part of the inner pipe 22 is perforated, the whole of the spinning solution must pass down the annular space and be subjected to the heating effect. in this way the solution is brought to a high degree of fluidity, with consequential advantage as regards the actual filtering. After filtration the solution passes through the inner pipe 22 and is insulated against cooling by the surrounding layer of spinning solution. The relatively low thermal conductivity of the spinning solution prevents any material change in the temperature of the solution as it passes through the inner pipe.

The lter body II, as is previously stated, is arranged in the corner of the spinning cell and is supported by the connecting pipes Il), I3. These pipes, particularly the pipe I3, may be insulated to prevent any local attemperation of the spinning solution therein. Furthermore, the interior of the filter body is readily accessible, and by removing the plugs 2| and 23 at each end of the outer casing 2B, all parts of the filter can be easily and completely cleaned. By reason of the provision of the unions 29, Sil, 33, 35, the filter body with or without the connecting pipes lil, i3 can readily be removed for cleaning purposes and for the changing of ltering material.

The arrangement described above includes a preliminary filtering body t. The provision of such a body enables a slightly smaller filter body Il to be employed, but if desired, the lter body 8 may merely serve the purpose of, or may be replaced by, a heat exchanger for a preliminary heating of the spinning solution.

An alternative arrangement is shown in Figure 4, in which the body 8 is dispensed with altogether and the supply pipe l leads through the top of the cell ii directly into the connecting piece 9 to which the pipes lll, i3 are connected. The

filter body Il is supported by the pipes iQ, i3, directly over the heating pipes i2 from which a current of hot air ascends to surround the filter body.

What I claim and desire to secure by Letters Patent isil. Apparatus for the production of extruded articial materials by the evaporative method comprising a spinning chamber, means in said chamber for heating evaporative medium in said chamber, a spinning jet for the extrusion of a spinning solution into such evaporative medium, and a filter member connected in series before said jet, and disposed in a position removed from the neighbourhood of said jet, and in the neighbourhood of said heating means.

2. Apparatus for the production of extruded artificial materials by the evaporative method comprising a spinning jet for the extrustion of a spinning solution into an evaporative medium, a preliminary filter body disposed above said jet and a main filter member connected in series between such preliminary filter and said jet, and disposed in a position removed from the neighbourhood of said jet.

3. Apparatus for the production of extruded artificial materials by the evaporative method comprising a spinning chamber, means in said chamber for heating evaporative medium in said chamber, a spinning jet for the extrusion of a spinning solution into such evaporative medium, a preliminary heating member disposed in the top of said spinning chamber for heating such spinning solution, and a lter member connected in series between said heating member and said jet, and disposed in a position removed from the neighbourhood of said iet, and in the neighbourhood of said heating means,

4. Apparatus for the production of extruded artiiicial materials by the evaporative method, comprising a spinning chamber, means in said chamber for heating evaporative medium in said chamber, a spinning jet for the extrusion of a spinning solution into such evaporative medium, and a lter member connected in series before said jet and disposed in a position removed from the neighborhood of said jet and in the neighborhood of said heating means, said filter member comprising an outer cylindrical casing, a perforated inner tube covered with a filtering medium, an inlet connection f'or leading the spinning solution to the inside of said outer cylindrical casing, and an outlet connection for leading the spinning solution away from the inside of said inner tube.

5. Apparatus for the production of extruded articial materials by the evaporative method, comprising a spinning chamber, means in said chamber for heating evaporative medium in said chamber, a spinning jet for the extrusion of a spinning solution into such evaporative medium, and a filter member connected in series before said jet and disposed in a position removed from the neighborhood of said jet and in the neighborhood of said heating means, said filter means comprising an outer cylindrical casing, an inner tube, an inlet connecti-on for leading the spinning solution to the inside of said outer cylindrical casing, and an outlet connection for leading the spinning solution away from the inside of said inner tube, said inner tube being perforated over a part of its length remote from said inlet connection and covered over its perforated part with a ltering medium.

6. Apparatus according to claim 5, wherein the outlet connection is formed at the end of the inner tube remote from the perforated portion of the tube so that the solution on entering the filter through the inlet connection is ycaused to traverse the length of the outer casing before reaching the perforated portion of the inner tube, and then to traverse the length of the inner tube before leaving the filter through said outlet connection.

2. Apparatus for the production of extruded artificial materials by the evaporative method, comprising a spinning chamber, means in said chamber for heating evaporative medium in said chamber, a spinning jet for the extrusion of a spinning solution into such evaporative medium, and a lter member connected in series before said jet and disposed in a position removed from the neighborhood of said jet and in the neighborhood of said heating means, said filter member comprising an outer cylindrical casing, a perforated inner tube disposed within said casing in such a manner as to leave an annular space between the outer casing and the inner tube, said tube being covered with a ltering medium, a removable plug closing one end of said outer cylindrical casing, a removable plug 'closing the corresponding end of the perforated inner tube, and a further removable plug disposed at the other end of the filter, said further plug closing the other ends of both the outer cylindrical casing and the inner tube while rallowing of the passage of spinning solution into the annular space between the outer casing and the inner tube, and out of the inner tube.

HENRY DREYFUS. 

